The identification of crops or weeds that provide semiochemicals beneficial to crops, such as repellents for the insect pests and/or attractants to natural enemies, is important for pest management in the field. Ovipositional preference and behavioral bioassays were conducted to determine suitable companion plants for sweet corn that will enhance repellency for the Asian corn borer (ACB), Ostrinia furnacalis Guenee (Lepidoptera: Pyralideae), or affect the common earwig [Euborelia annulipes Lucas (Dermaptera: Anisolabiidae)].
In oviposition preference tests, lemon grass (Cymbopogon citratus Stapf) and eggplant (Solanum melongena L.) produced the greatest oviposition deterrence. As an oviposition host, eggplant reduces the number of egg masses on corn and has potential as a trap crop in sweet corn production as it does not support larval growth. Larvae were found to be very mobile on oregano (Coleus aromaticus Benth.) and sweet potato (Ipomoea batatas L.) and quickly dispersed in silken threads, landing on the soil and dying. Associated weeds such as Mimosa pudica L. and Ageratum conyzoides L. proved toxic to larvae. Earwigs were not repelled by lemon grass, eggplant, oregano and the test weed species extract. Field trials must be conducted to verify that lemon grass and eggplant can serve as good companion crops for sweet corn.
Key Words: companion crop, larval growth, oviposition deterrence, oviposition preference, predation
INTRODUCTION
Companion planting and diversified planting utilize volatile plant chemicals which affect insect behavior. Companion planting is a cultural practice that uses plants with some insect repellent interspersed with other plants. The theory behind this practice is that the repellent action of the companion plants will impart some degree of protection to other plants. Most plants considered as companion plants are herbs or other plants that have volatile odors (e.g., marigold). Diversified planting takes advantage of the feeding preferences of insects, which locate food sources by shape, color and odor of the plants. Thus, mixing the plants helps decrease the attraction and the damage to the crops (Reeves 2001).
The Asian corn borer (ACB), Ostrinia furnacalis Guenee (